This invention relates to a method for manufacturing a frame for a dynamoelectric machine having heat dissipating fins, and more particularly, to a method for joining the heat dissipating fins and the frame main body.
A conventional method for manufacturing a dynamoelectric machine frame will be described taking an electric motor frame as an example.
Generally, when electromagnetic equipment is operated, the temperature of the equipment rises due to its internal power losses. When the temperature rise becomes excessive, the electrical insulation quickly deteriorates which may result in burn-out. For this reason, electric motors are provided with heat dissipating fins on the outer peripheral surface of the frame main body for increasing the air-contacting area to dissipate the inner heat to the exterior, thereby alleviating such temperature rise.
In conventional designs, the electric motor frame is made of cast iron or steel sheet.
However, a large amount of cast iron is needed in the case of the former, and a large amount of thermal energy is consumed for melting the cast iron, resulting in the disadvantage that the manufacturing costs are high.
On the other hand, in the case of the latter, as shown in FIGS. 5a and b, since rectangular heat dissipating fins 2 are welded at a joint 3 on the outer periphery of the frame main body 1 from diagonal direction, the inner periphery of the frame main body 1 is deformed by the thermal distortion due to the welding operation. Therefore, the inner diameter of the frame main body 1 must be machined prior to the insertion of a laminated iron core 5 having slots 4 which acts as a stator into the frame main body 1, resulting in the disadvantage that the manufacture of the frame is complex and expensive. Another disadvantage is its poor appearance due to the weld beads formed on the exterior thereof.